What kind of fishfinder are you using?? Sounds to me like there is a gap in the fishfinder - cuz you say the line "cuts into it", and you say the line snaps on the section the fishfinder is running on.
The fishfinders I use when I bait fish are molded plastic. They are nice and smooth on the inside and glide nice. I've seen some that look like they were "snapped" together, and I didn't buy them cuz I thought my line might get into the "crack"
If your line is always snapping on the leader where you have the fishfinder, I'd say the fishfinder - not the braid - is the problem.
Suggestion: Use 80# mono leaders. They are much thicker (so it won't get into the fishfinder's gap), won't ususally get cut by a blue (too thick except for the 15#+ gators), and is just as strong as your braid. Or, get some new fishfinders.
Let us know what you find. I use braid for chuncking with a fishfinder and haven't had the problem, so you've got me wondering.